/Engine/Plugins/Runtime/GameplayAbilities/Source/GameplayAbilities/Public/GameplayEffect.h
Copies SetbuCallerMagnitudes, but only if magnitudes don't exist in our map (slower but preserves data)
void MergeSetByCallerMagnitudes ( const [TMap](API\Runtime\Core\Containers\TMap)< [FGameplayTag](API\Runtime\GameplayTags\FGameplayTag), float > & Magnitudes )